Create a simple VI that accomplishes the acquire, analyze, and present tasks.

Transcription

1 Chalay Lesson 2 Navigating LabVIEW Simple AAP VI Goal Scenario Design Create a simple VI that accomplishes the acquire, analyze, and present tasks. You need to acquire a sine wave for 2 seconds, determine and display the average value, log the data, and display the sine wave on a graph. The input for this problem is an analog channel of sine wave data. The outputs include a graph of the sine data and a file logging the data. Flow Chart ACQUIRE ANALYZE PRESENT Acquire Data Display Data Log Data Determine Average Value Display Average Value Figure 2-1. Simple AAP VI Flow Chart LabVIEW Introduction Course Manual 2-46 ni.com

2 4. Save the VI as Simple AAP.vi. Select File»Save. Name the VI Simple AAP.vi. Click OK. Build a front panel similar to the one in Figure Figure 2-3. Acquire, Analyze and Present Front Panel 5. Place a waveform graph on the front panel to display the acquired data. If the Controls palette is not already open, select View»Controls Palette from the LabVIEW menu. On the Controls palette, select the Express category. Select the Graph Indicators category from within the Express category. Select the waveform graph. Place the graph on the front panel.

3 No Hardware Simulate the acquisition of a 100 Hz sine wave sampled at 1kHz for 2 seconds. Use the Simulate Signal Express VI. On the Functions palette, select the Express category. Select Input from the Express category. Select Simulate Signal from the Input category. Place the Simulate Signal Express VI on the block diagram. Wait for the Simulate Signal dialog box to open. Select Sine for the signal type. Set the signal frequency to 100. In the Timing section, set the Samples per second (Hz) to 1,000. In the Timing section, deselect Automatic for the Number of samples. In the Timing section, set the Number of samples to 2,000. Select the Simulate acquisition timing selection. Click the OK button. 9. Determine the average value of the data acquired by using the Statistics Express VI. Collapse the Express subpalette by selecting Express on the Functions palette. Select the Signal Analysis subpalette. Select the Statistics Express VI and drag-and-drop the Statistics Express VI to the block diagram to the right of the DAQ Assistant. Wait for the Statistics Express VI dialog box to open. Place a checkmark in the Arithmetic mean checkbox. Click OK.

4 10. Log the generated sine data to a LabVIEW Measurement File. Select Express on the Functions palette. Select the Output category. Select Write to Measurement File. Place the Write to Measurement File Express VI on the block diagram below the Statistics Express VI. Wait for the Write to Measurement File Express VI dialog box to open. Leave all settings as default. Click OK. Note Future exercises do not detail the directions for finding specific functions or controls in the palettes. Use the palette search feature to locate functions and controls. 11. Wire the data from the DAQ Assistant (or Simulate Signal Express VI) to the Statistics Express VI. Place the mouse cursor over the data output of the DAQ Assistant (or Simulate Signal Express VI) at the location where the cursor changes to the Wiring tool. Place the mouse cursor over the Signals input of the Statistics Express VI and click the mouse button to end the wire. 12. Wire the data to the graph indicator. Place the mouse cursor over the data output wire of the DAQ Assistant (or Simulate Signal Express VI) at the location where the cursor changes to the Wiring tool. Place the mouse cursor over the graph indicator and click the mouse button to end the wire.

5 13. Wire the Arithmetic Mean output of the Statistics Express VI to the Average Value numeric indicator. Place the mouse cursor over the Arithmetic Mean output of the Statistics Express VI at the location where the cursor changes to the Wiring tool. Place the mouse cursor over the Average Value numeric indicator and click the mouse button to end the wire. 14. Wire the data output to the Signals input of the Write Measurement File Express VI. Place the mouse cursor over the data output wire of the DAQ Assistant (or Simulate Signal Express VI) at the location where the cursor changes to the Wiring tool. Place the mouse cursor over the Signals input of the Write Measurement File Express VI and click the mouse button to end the wire. 15. Save the VI. Testing 1. Switch to the front panel of the VI. 2. Set the graph properties to be able to view the sine wave. Right-click the waveform graph and select X Scale»Autoscale X to deselect autoscaling. Right-click the waveform graph and select Visible Items»X Scrollbar. Use the labeling tool to change the last number on the X Scale of the waveform graph to Save the VI.

6 4. Run the VI. 5. Open the front panel of the VI by selecting Window»Show Front Panel. Click the Run icon on the front panel toolbar. The graph indicator should display a sine wave and the Average Value indicator should display a number around zero. If the VI does not run as expected, review the implementation steps. 6. Close the VI. LabVIEW Introduction Course Manual 2-56 ni.com